Delphi DLL

Verify XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Http, StringBuilder, BinData, XmlDSig;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
url: PWideChar;
http: HCkHttp;
sbXml: HCkStringBuilder;
verifier: HCkXmlDSig;
refUri: PWideChar;
jpgData: HCkBinData;
bVerified: Boolean;

begin
success := False;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// The XML containing the Signature to be verified contains the following:
// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <abc>
//   <xyz>
//     <jpg>
//         <name>starfish.jpg</name>
//         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
//     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>MbHOti6nOh9DJP/u7u1+a1u0wRYIGEdaAVk5ehxqeBhcR4qvGvCQ7wLxcfDuwFG2grSg43ANxDYngLqZTeFb5nCfywcuNBQI8FrNRVY5hkyv6kDW1BVN8ot9qPYX9oHxJp1e+nMszIiSxqHX3XDI7YnvFt/0CyeO5JaQQEzXzIwqqb8iUNcH/bJzR6CrTf1hGuQ5MPorG0bRwbYPPHHzipUqHBinK8VbHobnxL7GQHAhR8k9gDD35kZcMxf/74U7pGO19ZzTbdJW5S7q4bVVxvsuU3itTbhHI60pOE14ibrjZtIrPZLVUD3TQqIIF04TChW2NXdYOo3+ij4ZnP8x+g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
//   </xyz>
// </abc>

// The above XML is available at https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml
// First fetch the XML..

url := 'https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml';
http := CkHttp_Create();
sbXml := CkStringBuilder_Create();
success := CkHttp_QuickGetSb(http,url,sbXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

verifier := CkXmlDSig_Create();

// Load the XML containing the signatures to be verified.
// Note that this particular Signature already contains the RSA public key that will be used
// for verification.
success := CkXmlDSig_LoadSignatureSb(verifier,sbXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkXmlDSig__lastErrorText(verifier));
    Exit;
  end;

// Get the Reference URI, which in this case is the URL to the binary data that was hashed.
// This fetchs the URI attribute value from:  <ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg">
refUri := CkXmlDSig__referenceUri(verifier,0);
if (CkXmlDSig_getLastMethodSuccess(verifier) <> True) then
  begin
    Memo1.Lines.Add('No reference URI found.');
    Exit;
  end;

// Download the JPG data to be verified.
jpgData := CkBinData_Create();
success := CkHttp_QuickGetBd(http,refUri,jpgData);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

// Provide the JPG data to the verifier
CkXmlDSig_SetRefDataBd(verifier,0,jpgData);

// Verify the signature
bVerified := CkXmlDSig_VerifySignature(verifier,True);
Memo1.Lines.Add('Signature verified = ' + IntToStr(Ord(bVerified)));

CkHttp_Dispose(http);
CkStringBuilder_Dispose(sbXml);
CkXmlDSig_Dispose(verifier);
CkBinData_Dispose(jpgData);

end;